CEST-Dixon for human breast lesion characterization at 3 T: A preliminary study

Purpose: Chemical exchange saturation transfer (CEST) MRI for breast lesion characterization is promising. However, artifacts are prone to develop in breast CEST imaging as a result of strong lipid signals. The aims of the study are (i) to develop and validate the CEST-Dixon imaging sequence for simultaneous water-fat separation and B₀ mapping; and (ii) use the CEST-Dixon method to characterize suspicious lesions in patients undergoing percutaneous biopsy. Methods: The gradient-echo multi-echo Dixon acquisition is used to create fat-free CEST and B₀ maps. The sequence has been validated in phantoms and in vivo. Five healthy volunteers and 10 patients were scanned to compare the CEST contrast in three frequency ranges centered at 1, 2, and 3.5 ppm. The correlation between the CEST contrast and pathology markers (tumor type, estrogen receptor (ER) status, and Ki-67) was also investigated by stratifying the patients into ER-negative invasive ductal carcinoma (IDC) (more aggressive), ER-positive IDC (less aggressive), and benign groups. Results: The CEST-Dixon sequence shows homogenous fat removal in the water-only images. The ER-negative IDC tissues display a trend to higher CEST contrast in all three frequency ranges, whereas the ER-positive IDC, benign, and normal tissues have lower CEST contrast. No significant differences were observed among the ER-positive IDC, benign, and normal tissues. Of the three frequencies ranges, the CEST contrasts at 1 ppm are high in the ER-negative IDC group, have the largest difference among the ER-negative IDC and the other groups, and have the highest correlation with Ki-67. Conclusion: Breast CEST-Dixon imaging shows potential to differentiate more aggressive from less aggressive cancers. Magn Reson Med 80:895–903, 2018.